Organic condensation products derived from halomethylated diaromatic ethers as well as from poly(methylol diaromatic ethers) to produce poly(methylene diaromatic ethers) are described in several U.S. patents, namely, U.S. Pat. Nos. 2,911,380, 3,004,072, 3,000,839, 3,269,973 and 3,342,873. The polymers, prepared in accordance with these patents, have good thermal stability and are useful in molding, potting and film forming. The techniques for their preparation described in the literature, including the patent literature above set forth, have suffered from the by-product halogen acid produced at one stage or another. The production of the halogen acid creates a handling problem during manufacture as well as the difficulty in removing the traces of the acid from the final product.
Another difficulty with the prior art techniques is that the monomers are not readily formed into prepolymers which are more economical to employ as well as more precise in applications such as molding and potting than monomeric-containing formulations.
The present invention differs from the prior art in field of conventional aromatic formaldehyde precursor resins by employing as the starting precursor a methoxy functional aromatic ether mixture which is reacted with a phenolic compound, with formaldehyde, to yield either a heat curable (thermosetting resin) or with or without formaldehyde to yield thermoplastic resin which may be subsequently thermoset with a formaldehyde donor (i.e., hexamethylene tetraamine). The ether functionality is unique because it is intermediate the polymeric structure as well as terminal, thus providing reactive sites within the polymer precursor for a different structural characteristic than resins prepared from the art-taught precursors. For example, the product of the present invention can be compared with numerous art references in the following manner:
Precursor:
This invention - The result of reacting an aromatic hydrocarbon, e.g., naphthalene or diphenyl oxide, hereafter A, with a formaldehyde-yielding compound, e.g., formaldehyde or paraformaldehyde, and an alcohol, e.g., methanol, to yield a mixture of methoxy functional ether alkyl aromatics, such as EQU A--CH.sub.2 OCH.sub.3, CH.sub.3 OCH.sub.2 --A--CH.sub.2 OCH.sub.3, EQU a--ch.sub.2 och.sub.2 och.sub.3, a--ch.sub.2 och.sub.2 och.sub.2 --a--ch.sub.2 och.sub.3, EQU ch.sub.3 och.sub.2 --a--ch.sub.2 --a--ch.sub.2 och.sub.2 --a--ch.sub.2 och.sub.3,
for example, most of which have been identified by analysis.
The prior art - Represented by Krzikalla et al., U.S. Pat. No. 2,954,360, Kester, U.S. Pat. No. 2,330,827, Rosen, U.S. Pat. No. 2,237,634, Imoto, U.S. Pat. No. 3,165,558, Nastukoff, U.S. Pat. No. 1,827,538, Harris et al., U.S. Pat. No. 3,787,350, Kakiuchi et al., U.S. Pat. No. 3,303,167, Erich, U.S. Pat. No. 2,914,579, Brachel, Canadian Pat. No. 654,676, Harris et al., and British Pat. No. 1,228,778 each discloses the reaction of formaldehyde with an aromatic hydrocarbon. These representative patents of the art each produce a precursor having the following probable structure wherein A is the aromatic hydrocarbon moiety: ##STR3##
The products have oxygen contents from about 5 to 12 percent depending upon the starting aromatic, the ratio of formaldehyde to aromatic, and, the degree to which the condensation is carried out.
Some of this considerable art teaches the use of methanol during the preparation of the aromatic hydrocarbon-formaldehyde condensation product. Until now the alcohol, however, has been considered to merely etherify the resulting hydroxyl groups of the classic condensation product reducing the number of terminal hydroxyl moieties available for reacting with the activated hydrogens of the aromatic reactant to form methylene bridges. It also has been shown, Zinke and Ziegler, Weiner Chemiker Z. 47, 151 (1944) and Wegler, Z. Angew. Chem. A 60, 88-96 (1948) that internal ethers of the aromatic methylol intermediates can be produced under certain conditions.
The Erich U.S. Pat. No. 2,914,579, discloses these aspects of aromatic-aldehyde reactions, but does not teach more, preferring to illustrate the advantages of using xylenes and capping the aromatic methyl hydroxy moiety to the methylol moiety to reduce condensations. The reference never employs methanol in quantities sufficient to obtain the inner ether-polyether intermediates which are obtainable in accordance with the present invention. The reference employs 5-12 percent by weight alcohol based on formaldehyde which for the xylene employed is a ratio of 1/30 mole maximum of alcohol per mole of xylene (maximum ratio 1 mole xylene per mole formaldehyde and 5 to 12 percent by weight alcohol based on formaldehyde 0.12 .times. 30/106 = 1/30 mole alcohol per mole xylene) as compared to the hereinafter-disclosed range of 0.3 to 10 moles alcohol per mole of aromatic. The amount of alcohol employed by the reference is less than 1/10 that hereinafter employed which accounts for the different reaction product hereinafter obtained as compared to the patent.
Imoto et al., U.S. Pat. No. 3,165,558, discloses that 1-4 alkyl substituted aromatic hydrocarbons react with formaldehyde to produce an ". . . oxygen-containing factor of the resin (which) is due to ether (--CH.sub.2 O--CH.sub.2 --) and acetal (--CH.sub.2 O.multidot.CH.sub.2 .multidot.OCH.sub.2 --) bonds which bind the aromatic hydrocarbon nucleus . . . ". The oxygen contents of these resins are below 10 percent. This resin intermediate differs from that of the present invention in that the oxygen content is lower and methanol is not employed.
Kakiuchi et al., U.S. Pat. No. 3,303,167, discloses the same background as Imoto et al. above, then proceeds to described a procedure to prepare benzene or toluene aldehyde resins by using high concentrations of formaldehyde or polymers of formaldehyde in water, i.e., 3-15 percent water. The formaldehyde is also employed in a high concentration with respect to the aromatic hydrocarbon, i.e., 1-5 moles formaldehyde per mole of aromatic. The oxygen content of the product of these reactions is 7.5-20 percent and their molecular weight is 280 to 380.
Japanese Patent 45-38074 discloses use of small amounts of alcohol similar to Erich above, i.e., 20 g per 300 g xylene, 18 g per 400 g mesitylene, 10 g per 390 g naphthalene. The results of this patent appear to be similar to Erich's results. The amounts of alcohol are in the same mole ratio range as Erich, viz., 4.5 moles xylene per mole alcohol (0.2 mole alcohol/mole xylene) is the maximum.
These references all disclose the products of conventional aromatic hydrocarbon-aldehyde reactions. The acetal and ether linkages are few in number being only those derived from the occasional condensation of the methyloyl moieties probably according to ##STR4##
Representative of other patents which disclose oxygen-containing aromatic aldehyde resins, i.e., oxygen contents 3-12 percent, obtained by various techniques are U.S. Pat. Nos. 2,954,360; 2,330,827; 2,237,634; 3,787,350; and 1,827,538; Canada Pat. No. 654,676 and British Pat. No. 1,228,778. Each of these references obtains its oxygen content through the chance reaction of two methylol groups to produce the ether or acetal linkage.